Photons are electromagnetic waves. They exhibit particle-like qualities in many situations and have zero rest mass.
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If photons have no mass, how can they have momentum?
As an explanation of why a large gravitational field (such as a black hole) can bend light, I have heard that light has momentum. This is given as a solution to the problem of only massive objects ...
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7answers
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How can a photon have no mass and still travel at the speed of light?
I've read a number of the helpful Q&As on photons that mention the mass/mass-less issue. Do I understand correctly that the idea of mass-less (a rest mass of 0) may be just a convention to make ...
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5answers
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Why can't photons have a mass
Why can't photons have a mass? Could you explain this to me in a short and mathematical way?
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2answers
700 views
Does $E = mc^2$ apply to photons?
Photons are massless, but if $m = 0$ and $E = mc^2$ then $E = 0c^2 = 0$. This would say that photons have no energy, which is not true.
However, given the formula $E = ℎf$, a photon does have energy ...
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3answers
720 views
Is a photon “fixed in spacetime”?
From what I've read, according to relativity, a photon does not "experience" the passage of time. (Can we say there is no past/present/future for a photon?)
Would it be better to say a photon is ...
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4answers
424 views
What is the mechanism behind the slowdown of light/photons in a transparent medium?
So light travels slower in glass (for example) than in a vacuum. What causes light to slow down? Or: How does it slow down? If light passes through the medium, is it not essentially traveling in the ...
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3answers
579 views
Anti-laser: How sure we are that energy is transported?
Reading this PE question
can-we-transport-energy-over-infinite-distances-through-vacuum-using-light, a related question arises naturally:
Is energy transported (by light)? -- (I did believed in this ...
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5answers
962 views
How are forces “mediated”?
I hope this is the right word to use.
To me, these forces seem kind of fanciful (except for General Relativity and Gravity, which have a geometric interpretation).
For example, how do two charged ...
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4answers
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What exactly is a quantum of light?
I am currently trying to learn some basic quantum mechanics and I am a bit confused. Wikipedia defines a photon as a quantum of light, which it further explains as some kind of a wave-packet.
What ...
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5answers
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Do photons gain mass when they travel through glass?
Please correct me if I'm wrong, but I believe that photons slow down when travelling through glass. Does this mean they gain mass? Otherwise, what happens to extra kinetic energy?
I understand now ...
7
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1answer
562 views
What are the specific requirements for a do-it-yourself quantum double-slit experiment?
I was shocked to recently learn that the double-slit experiment is not only possible to do with completely ordinary equipment (with photons of course), but it actually looks rather easy. This is from ...
9
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3answers
337 views
How does a photon experience space and time?
To an an external observer it appears that time has stopped for photon. But this relation is reflexive, so for an observer travelling with the photon it appears the universe has stopped everywhere.
...
9
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3answers
892 views
Does a photon have a rest frame?
Quite a few of the questions given on this site mention a photon having a rest frame such as it having a zero mass in its rest frame. I find this contradictory since photons must travel at the seed of ...
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2answers
150 views
Is it possible to charge photons
For example there are anti-particles to every particle we know,
Similary in some sense, is there a possibility that we can charge photons..if not what are the reasons and has there been any attempt ...
6
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4answers
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Spontaneous pair production?
So I've been looking into particle-antiparticle pair production from a gamma ray and don't understand one thing.
Let's say I have a 1,1 MeV photon and it hits a nucleus - electron-positron pair with ...
6
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2answers
498 views
Tachyon and Photons
Is there a particle called "tachyons" that can travel faster than light? If so, would Einstein's relativity be wrong? According to Einstein no particle can travel faster than light.
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1answer
376 views
If photons are deflected by a strong gravitational field, then how come photons do not have mass? [duplicate]
Possible Duplicate:
Explain how (or if) a box full of photons would weigh more due to massless photons
It has been proved and showed through experiments that light can be bent by the Sun or ...
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5answers
2k views
Does a photon interfere only with itself?
I sometimes hear statements like that:
Quantum-mechanically, interference pattern occurs due to quantum interference of wavefunction of a photon. Wavefunction of a single photon only interferes ...
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3answers
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Compton scattering vs. photoelectric effect
Say a photon hits some atom.
What determines whether there will be a photoelectric effect (photon is absorbed, electron is released) or whether there will be a Compton scattering (the photon is ...
3
votes
3answers
680 views
What are electromagnetic fields made of?
I am trying to understand electromagnetic fields so I have two question related to them.
What is a electromagnetic field made of? Is it made of photons / virtual photons?
How about a static electric ...
3
votes
4answers
582 views
What if we could give photons some mass?
I was reading an article and these paragraphs got me wondering...
Before I list the replies, here is some background. The Higgs mechanism describes an invisible field that, it is argued, split one
...
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3answers
957 views
How is light affected by gravity?
Light is clearly affected by gravity, just think about a black hole, but light supposedly has no mass and gravity only affects objects with mass.
On the other hand, if light does have mass then ...
9
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1answer
99 views
If light is linearly polarized, does it have some spatial extent?
If light (a photon) is linearly polarized, say vertically, does it have some vertical spatial extent (perhaps in amplitude)?
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4answers
673 views
Why photons transfer to electrons perpendicular momentum?
Linear antenna directed along z, photons (EM waves) propagate along x. Momentum of photons have only x component. Why electrons in antenna have z component of momentum?
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4answers
174 views
slit-screen and wave-particle duality
In a double-slit experiment, interference patterns are shown when lights pass through slits and illuminate the screen. So, the question is if one shoots a single photon, does the screen show ...
3
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2answers
530 views
Propagation of light in transparent media: absorption and reemission or scattering?
In the two Phys.SE questions What is the mechanism behind the slowdown of light/photons in a transparent medium? and Why glass is transparent? transparent media were discussed. But I'd like to clarify ...
2
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3answers
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Can a photon be made to orbit a known (or undiscovered theoretical) body?
Can a photon through some process be made to orbit a celestial or any other object?
Two follow-up questions.
Can this orbit be described as the photon crossing its own path.
Will this ...
2
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2answers
361 views
Is Time Significant in the Double Slit Experiment
When doing the classic double slit experiment is the time between emitting photons significant at all? Say, a single photon is emitted, the scientist waits T seconds, then emits another photon. Are ...
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1answer
102 views
Specific electron energy gap values $E_{i+1}-E_i$ vs. photons with arbitrary energy $\hbar \omega$
The energy levels of electrons in an atom are quantized $E_i$. A photon of a specific momentum $\vec p$ and energy $$\omega=(E_{i+1}-E_i)/\hbar$$ hits an atom and gets absorbed. Okay now say the ...
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2answers
584 views
Producing photons with same frequency, different amplitude wave
I don't understand how two photons of the same frequency can have different amplitudes, neither how to produce them.
I know that classically the square of the amplitude is proportional to the energy, ...
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vote
2answers
324 views
Is energy exchange quantized?
In the photoelectric effect there is a threshold frequency that must be exceeded, to observe any electron emission, I have two questions about this.
I) Lower than threshold:
What happen with lesser ...
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1answer
463 views
Neutrinos vs. Photons: Who wins the race across the galaxy?
Inspired by the wording of this answer, a thought occurred to me. If a photon and a neutrino were to race along a significant stretch of our actual galaxy, which would win the race?
Now, neutrinos ...
8
votes
4answers
408 views
What longest time ever was achieved at holding light in a closed volume?
For what longest possible time it was possible to hold light in a closed volume with mirrored walls?
I would be most interested for results with empty volume but results with solid-state volume may ...
12
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1answer
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How are photons “consumed”?
I have very little background in physics, so I apologize if this question is painfully naive.
Consider the following thought experiment: an observer is in a closed room whose walls, floor, and ...
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4answers
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When lasers are used to cool atoms or ions, etc where does the heat go?
According to the first law of thermodynamics, sourced from wikipedia
"In any process in an isolated system, the total energy remains the same."
So when lasers are used for cooling in traps, similar ...
8
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1answer
153 views
How the inverse square law in electrodynamics is related to photon mass?
I have read somewhere that one of the tests of the inverse square law is to assume nonzero mass for photon and then, by finding a maximum limit for it , determine a maximum possible error in ...
6
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3answers
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Properties of the photon: Electric and Magnetic field components
Consider an electromagnetic wave of frequency $\nu$ interacting with a stationary charge placed at point $x$. My question concerns the consistency of two equally valid quantum-mechanical descriptions ...
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4answers
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Why don’t photons interact with the Higgs field?
Why don’t photons interact with the Higgs field and hence remain massless?
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5answers
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Can you split a photon?
I was wondering if a photon is divisible.
If you look at a photon as a particle, then you may be able to split it (in theory).
Is it possible and how do you split it?
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2answers
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Deriving Planck's radiation law from microscopic considerations?
In the usual derivation of Planck's radiation law, the energies or frequencies $\omega$ of the oscillators depend on the measurements $L$ of the black body. The model is such that the only ...
4
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3answers
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Precision of Coulomb's law
Up to which precision has the coulomb law proven to be true?
I.e. if you have two electrons in a vacuum chamber, 5 meters appart, have the third order terms been ruled out? Are there any theoretical ...
4
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4answers
711 views
What happens when a photon hits a mirror?
When a photon of light hits a mirror does the exact same photon of light bounce back or is it absorbed then one with the same properties emitted? If the same one is bounced back does it's velocity ...
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2answers
357 views
Is photon emission possible without electrons changing energy levels?
Does molecular vibrational transition and consequent emission of infrared radiation involve electrons changing energy level? In wikipedia, about vibronic transitions it says "Most processes leading to ...
3
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1answer
334 views
Does the potential energy for a given photon increase or decrease in quanta?
As a photon leaves a strong gravitational field, it loses energy and redshifts. Is the exchange in potential energy of a photon characterized by energy quanta?
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2answers
181 views
What is light, and how can it travel in a vacuum forever in all directions at once without a medium?
I know there are many questions that are similar (maybe identical?). I am not a physicist nor a student - I am just interested in physics and have been watching many physics channels on youtube ...
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3answers
206 views
Mechanism for the gravitational field generated by photons
This question follows from a schooling I received in this thread.
I figured that photons do not interact with gravity, except when they've spontaneously converted into a particle-antiparticle pair. ...
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1answer
419 views
Can a photon exiting from a gravity well ever reach a frequency of zero / wavelength of $\infty$?
In reading another question about gravity's effects on a photon, I wondered if it were possible for a photon to ever be redshifted to zero wavelength.
I know that black holes have a gravity field ...
0
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2answers
392 views
Can photons and gluons be holes in an aether?
Consider photons and gluons have 0 mass and 0 charge. In many respects they're already understood as the absence of a particle by mathematical models. Couldn't this be interpreted to mean they ...
5
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2answers
384 views
photons in expanding space: how is energy conserved?
If a photon (wave package) redshifts (streches) traveling in our expanding universe, is it's energy reduced? If so, where does it go?
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2answers
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Photon statistics of an incandescent light source
We usually calibrate the cameras on our microscopes by capturing 20 images of a blurry (not sharp) fluorescent particle. For each pixel in this stack of 20 images we calculate the intensity variance. ...
